1. Field of the Invention
The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus capable of automatically separating an image of a specific color and forming a superposed multi-color image.
2. Related Background Art
As an image forming apparatus for reproducing an image having the same color as that of an original, there is known a full color copying machine. A full color machine is expensive and requires maintenance. As a more simpler color image forming apparatus, there is disclosed in U.S. Pat. No. 4,711,553 a color copying machine for copying an original image with black, red, blue and the like by recognizing color components of the original such as red and blue.
With this color copying machine, an original image is optically projected onto a photosensitive member. The red component area of the original image is discriminated, and the red component area of a latent image formed on the photosensitive member is erased with a laser beam or the like. Thereafter, the remaining latent image is developed with black toner and transferred to a recording paper. This time, the original image is again optically projected to the photosensitive member. The area other than the red component area of the latent image formed in the photosensitive member is erased with a laser beam. Thereafter, the remaining latent image is developed with a red toner, and transferred to the recording paper in superposition with the image previously transferred. In this manner, the original image is copied using black and red colors.
With the color copying machine of this type, however, a proper two color image cannot be reproduced because it has only poor precision in erasing an area of a latent image of a specific color.